The present invention is directed to a conditioning shampoo formulation having a high surfactant level suitable for preconditioning thinning hair prior to treatment with a hair restorer. The formulation is further characterized by comprising three main ingredients: (1) a fatty alcohol sulfate such as triethanolamine lauryl sulfate or sodium lauryl sulfate and/or a fatty alcohol ether sulfate such as sodium laureth sulfate; (2) cocamidopropyl betaine and (3) cocamide diethanolamine, which are formulated in the absence of addtional preservative compounds.
Shampoos are a mixture of various types of surfactants which impart different characteristics to the final product. In general, a shampoo contains a base surfactant(s) for cleansing at 10-15% (w/w), a foam booster at 3-5% (w/w), a conditioning agent at 3-5% (w/w), small amounts of chelating agents, viscosity and pH adjusters, preservatives, fragrance, miscellaneous "nutritive" ingredients, and water.
The base surfactant is usually a salt of a C.sub.12 -C.sub.14 alkyl sulfate, alkyl ether sulfate, or alkyl olefin sulfonate, depending on the mildness and foaming characteristics desired. "Baby" shampoos and "extra gentle" shampoos will usually use an emphoteric, nonionic, or sulfosuccinate as a base surfactant. The foam boosters are primarily C.sub.12 -C.sub.14 fatty alkanolamide surfactants derived from coconut oils. The conditioning agents generally are substantive to the hair and frequently serve a dual role as a foam booster. Cocamidopropyl betaine and coconut oil derived amine oxides are typical examples of surfactant based conditioning agents. Hydrolyzed animal protein, keratin, and collagens have been popular conditioning agents for many years. The base surfactants and conditioning agents are usually sold as solutions in the range of 20-40% (w/w). The percentages specified above are on the "as is" basis as purchased from the supplier rather than on the "active" basis. Thus, the percentages specified above may contain a substantial amount of water.
Due to the nature of the composition, a shampoo is usually a good medium to support microbial growth. Since most surfactants used in the manufacture of shampoos are sold as aqueous solutions or pastes, which are rarely more than 40% (w/w) on the active basis, they will support microbial growth and are frequently preserved with trace levels of formaldehyde by the supplier. The foam boosters and conditioning agents provide a good nitrogen source to the microbes in the aqueous enviroment of the shampoo which is typically greater than 80% water. Proteins and "nutrient" ingredients are particularly good microbial growth promoters and a present a challenge to selection of an effective preservative system. Surprisingly, the subject formulation is high in surfactant but does not support microbial growth and, therefore is self-preserving without the addition of traditional preservatives.